(a) Field of the Invention
The present invention relates to a method and system for setting a TCP (Transmission Control Protocol) proxy to reduce a packet loss and a transmission delay during a handover in an Internet network. More specifically, the present invention relates to a method for eliminating a packet loss and a transmission delay in a long-term disconnection situation caused by the handover of a mobile station because a split connection TCP is applied to the mobile station using a terminal connection TCP proxy only during a handover of the mobile station in a wire/wireless integrated IP network.
The present invention is also related to a TCP control during a handover in a wireless IP network, and more particularly, to an apparatus for packet transmission in a wire/wireless integrated network that performs a TCP for preventing a deterioration of network performance by a TCP performing a congestion control technique to lower the packet transmission rate of a transmitter (server) on the assumption that congestion causes a packet loss on the wireless link.
(b) Description of the Related Art
Assuming that a packet loss results from congestion, the TCP slow-start and congestion control according to the prior art is applied to reduce the threshold of a retransmission timeout of a transmitter to half of the size of a congestion control window, set the size of the congestion control window to “1”, and initiate the slow-start.
This process is applied equally to packets lost or delayed during a handover of a mobile station due to the handover, as well as to congestion on the wireless link. Hence, the TCP of the transmitter unnecessarily reduces the size of the transmitter congestion control window to “1”, wasting a wire link resource.
Many approaches have been developed to improve this problem. Those approaches can be classified into two methods, as follows.
One method is modification of a TCP between terminals, and the other provides a TCP proxy in the middle of a packet path between two terminal systems connected to each other through a TCP connection.
The TCP modification method has the difficulty in implementation in an actual situation because all the existing terminals established as a wire infrastructure should be modified in the TCP modification method. The other method is an approach widely used to overcome the difference between different network environments that relates to a split connection TCP (or an indirect-TCP) between a transmitter (hereinafter referred to as “server”) and a final receiver (hereinafter referred to as “mobile station”). In the split connection TCP, the base station is designated as a wire/wireless link separation unit acting as a TCP proxy that receives a packet transmitted from the server to the mobile station, transmits an acknowledgement (hereinafter referred to as “ACK”) message to the server on behalf of the mobile station, and buffers a packet received from the server. Therefore, the base station serves as a transmitter in charge of reliable packet transmission to the mobile station. This method enables many wireless TCPs to use the proxy with advantages of a local restoration function and a disconnection processing function.
However, the split connection TCP is based on transmission errors caused by the wireless environment with no consideration of a long-term disconnection situation such as a handover of the receiver, resulting in difficulty in completely eliminating a packet loss and a transmission delay occurring during a handover of the mobile station. In addition, the base station must serve as a TCP proxy for all the mobile stations belonging to its cell which causes an overload such as overflow.